Because these out of place things were almost never created by human but given as gifts by Gods/Aliens/Other dimensional beings. So they now have access to a pl

Because these out of place things were almost never created by human but given as gifts by Gods/Aliens/Other dimensional beings. So they now have access to a plane and a limited knowledge on how to operate it, but they can't recreate it or use its tech. to start building cars/trains. Once the given artifact broke down, it simply got lost to dust over next few centuries.